When particles floc together

We are all familiar with the phrase 'birds of a feather flock together', meaning that those of similar tastes congregate in groups. Flock has two meanings, however. One applies to a group of animals or birds or people, and the other to tufts of wool, eg as in flock wallpaper. The latter use comes from the Latin floccus, which means a tuft of wool, and flocculus means a little tuft. 

We now use floc to mean the rather fuzzy particles produced when a solute comes out of solution and clumps together. The process is called flocculation.